Sun & Skin
Can you tan on a cloudy day? What clouds really do to UV
What each cloud type does to UV
| Sky | UV that gets through | Tanning reality |
|---|---|---|
| Thin / high cloud (haze, cirrus) | 80–95% | Almost full strength — classic "how did I burn?" weather |
| Scattered / broken cloud | 60–80% — with spikes above 100% | Cloud edges reflect extra UV downward |
| Solid overcast | 20–40% | Slow tanning still possible on long exposure |
| Dark rain clouds | 10–20% | Effectively protective |
The reason people burn on cloudy beach days is simple: clouds block the heat (infrared) far more effectively than they block UV. Your warning system — feeling hot — switches off while the radiation keeps coming. Sand and water reflection add another 10–25% on top.
So how do you know if today tans?
Ignore the sky, read the number. If the live UV index shows 3 or higher, melanin production is on — that's the whole logic behind the UV 3–5 tanning window, and it applies identically under haze. Every city page shows the cloud-adjusted UV right now and hour by hour: London, Seattle, Amsterdam — or search your own. Planning ahead? The tomorrow forecast includes expected cloud.
Frequently asked questions
Can you tan through clouds?
Yes - light cloud passes 80-95% of UV and solid overcast still passes 20-40%. If the UV index is 3 or higher, your skin responds.
Can UV be higher on a partly cloudy day than a sunny one?
Briefly, yes. Broken clouds reflect extra UV toward the ground at their edges - measured spikes go above the clear-sky value.
Why do people burn more on cloudy days?
Clouds block heat better than UV, so you don't feel the exposure - and stay out longer without protection.
Do I need sunscreen on a cloudy day?
If the UV index is 3 or higher, yes - the same rule as sunny days. Check the live number rather than the sky.
Can you tan through a window?
Standard glass blocks UVB but passes much of UVA - so meaningful tanning is unlikely, but long exposure still ages skin. Full breakdown: can you tan through a window?
Live index, burn time for your skin type, and the best hours to be outside.
Sources & further reading